The incorporation of flavorants in tobacco products is an important development in the tobacco industry due to the lowered aromaticity of the available tobacco and to the increased preference of some smokers for filter cigarettes and low delivery cigarettes. The addition of certain desirable flavorants to tabacco is limited by their volatility which causes them to be lost or diminished in quantity during processing and storage of the tobacco product. This problem is even more acute for filter cigarettes containing active adsorbent, such as charcoal, in the filters. During the processing and storage of this type of product, volatile flavorants migrate from the tobacco and are irreversibly bound by the active adsorbent, thereby depleting the flavorant in the product and possibly altering the effectiveness of the active adsorbent in its selective removal of undesirable smoke components.
Menthol is a flavorant which has received high acceptance as an additive to tobacco products because of the pleasant cooling effect and desirable aroma and flavor characteristics which it imparts to the smoke. Its high degree of volatility and ease of sublimation have presented problems in the manufacturing operations and, in addition, have resulted in a decreased shelf-life of the product due to losses of menthol by diffusion on storage.
In an attempt to alleviate these problems, it has been suggested that menthol might be adsorbed on a suitable support, such as activated charcoal or fuller's earth, and that the resultant composition might then be added to the tobacco. Attempts to pursue this method have not been satisfactory. The menthol yields from such adsorbents have been found to be very low. Moreover, this method obviously necessitates incorporation of the adsorbent into the tobacco, and such a foreign material can result in an undesirable appearance as well as give rise to uneven burning of the tobacco.
In order to overcome these difficulties, menthol has been incorporated into the tobacco as a part of a compound (i.e., a menthol-release agent) in such form that upon burning of the tobacco, the compound is decomposed to yield the desired menthol flavorant. While considerably more satisfactory than earlier attempts, even this technique has evidenced certain drawbacks.
Bavley et al, U.S. Pat. No. 3,312,226, describes a process whereby menthol is incorporated into tobacco as the carbonate ester of various alcohols, particularly one such as linalool, which are themselves useful flavorants. Upon pyrolysis of these carbonate esters, incident to the normal burning temperatures of the tobacco, the menthol is released to flavor the smoke. However, these simple carbonate esters have not proven wholly satisfactory. They retain one of the difficulties of menthol itself, in that they are somewhat susceptible to migration in the tobacco, and thereby prevent the strict control of quantitative release of menthol to the tobacco smoke during burning. Additionally, the second alcohol of the carbonate ester can prove susceptible to chemical alteration during pyrolysis, thus giving rise to undesirable chemical fragments which can add a chemical aftertaste to the smoke.
The Mold et al U.S. Pat. Nos. 3,332,428 and 3,419,543, offer a slightly different approach to the problem of adding menthol flavor to a tobacco smoke. These patents, like that of Bavley et al, rely upon the formation of a carbonate ester to bind the menthol in a release agent. Here, however, a polyhydroxy compound such as monosaccharide, disaccharide, trisaccharide, polysaccharide, or glycol is used to fix the menthol in the tobacco. Again there are certain drawbacks. Because the alcohol linkages of these saccharides and glycols are only primary or secondary in character, the efficiency with which the menthol can be regenerated upon pyrolysis is limited.
The Rundberg, Jr. et al U.S. Pat. No. 3,887,603 describes the development of a new type of menthol-release agent for imparting menthol flavor to tobacco smoke with a high efficiency of menthol release upon pyrolysis under normal smoking conditions. The menthol-release agent is a polymeric l-methyl carbonate ester composition characterized by the presence of a tertiary alcohol ester attachment.
In addition to menthol, a variety of other flavorants have been developed and proposed for incorporation into tobacco products. Illustrative of such tobacco flavorants are those described in U.S. Pat. Nos. 3,580,259; 3,625,224; 3,722,516; 3,750,674; 3,879,425; 3,881,025; 3,884,247; 3,890,981; 3,903,900; 3,914,451; 3,915,175; 3,920,027; 3,924,644; 3,937,228; 3,943,943; 3,586,387; and the like. The tobacco flavorants include compounds such as succinic anhydride; dihydroxyacetone; substituted pyridines; cinnamic derivatives; isovaleric acid; 6-methylhepta-3,5-diene-2-one; 2-butyl-2-butenal; 1,2-cyclohexanediene, alpha-pyrones; substituted butyrolactones; pyrazines and thiazolidines; and the like.
U.S. Pat. No. 3,139,888 suggests the use of isoprenoid alcohols to impart desirable flavor to tobacco. U.S. Pat. No. 3,589,372 recommends the incorporation of a polyisoprenoid hydrocarbon into tabacco products as a flavor enhancer.
The use of the diverse types of tobacco flavorants is characterized by various disadvantages. Some flavorants are prohibitively expensive. Other flavorants are complex mixtures of variable constituency and are inconsistent in effect. Other flavorants are too volatile for cigarette packaging and storage purposes. Still other prior art flavorants have a flowery fragrance which impart undesirable aroma characteristics to tobacco products or which do not adequately improve the taste, character, and flavor of smoking tobacco.
Accordingly, it is a main object of this invention to provide a tobacco flavorant which is characterized by lack of mobility and/or volatility at ambient temperature when incorporated in a tobacco composition.
It is another object of this invention to provide a novel polymeric composition which is adapted to release alcohol flavorant of enhancing character to tobacco smoke under normal smoking conditions, with optimal efficiency and without masking of the natural flavor of the resultant main stream tobacco smoke.
It is a further object of this invention to provide a polymeric composition which is adapted to release menthol to tobacco smoke under normal smoking conditions with nondeleterious effect on the flavor of the resultant tobacco smoke.
Other objects and advantages of the present invention shall become apparent from the following description and examples.